With great corrosion resistance and mechanical property, ferrite-austenitic duplex stainless steels have been applied to many components in corrosive environments such as sea water pumps. Due to different coefficients of thermal expansion and elastic moduli between the two phases, plastic deformation and phase stress will occur during heat treatment history in material processing such as casting, forging or annealing, which may affect material properties such as fatigue strength, welding stability and so on. In this study, strain-free lattice constants of both phases were measured from strain-free reference samples, which were carefully prepared as electropolished thin plates with thickness of lower than 90 micrometer, nearly equal to the grain size of austenitic phase. Phase stress distribution along the thickness direction of hollow cylinders fabricated by centrifugally cast duplex stainless steel was measured by pulsed neutron diffraction using time-of-flight (TOF) method at Japan Proton Accelerator Research Complex (J-PARC). Based on these results, the mechanism of stress development during centrifugal casting and the effect of stress relief heat treatment (SRHT) were discussed.